LOOKING FOR GOLDSCAN 4 Schematic.

[aft_72005]

btw... i already "transfered" previous pcb draw into SL5, just to have better control over it and to much more easily perform some checks.
This is just first step in process of drawing new board.
Enjoy:

very good

[pustareka]

Привет !

Подлинная временная диаграмма Голдскан 4 от Эрика Фостера
https://prnt.sc/yWrkootebwf0

Google say:
Genuine time chart Goldscan4 from Eric Foster
https://prnt.sc/yWrkootebwf0

[ZOUjiarui]

What is the principle?

[ZOUjiarui]

Both sides of the resistor are -12

[GeoMax]

Hi,

if you take a closer look at the schematic again you will see that the resistor is connected between -12v and -12. This are two different voltages.

[Alexismex]

Zoujiarui, It is for stabilize the voltage (Decoupling with one resistor and one capacitor)...

[ZOUjiarui]

Thanks, I see. Then here should be c18, looks like c10

[ivconic]

Ok, I've been putting off making the Goldscan IV detector for years. For various reasons. And I finally decided to do it.
I read in detail the existing threads and everything written by colleagues who have already made it.
Everything is set up according to the instructions.
As "targets" for testing I used ancient Roman coins:
1) "Antoninianus",
2) "Sestertius" and
3) a bronze applique/buckle.

And from iron;
1) "modern" pliers and
2) nail from the 5th century.

I used an antique brick piece from the 5th century to check and adjust the GEB.

And the detector works as you will see in the video.
I have a few questions/complaints. Maybe one of you has the right answers, advice.

1) In the "Off" mode, it is very deep (it is not shown the "Off" mode on the video), while in the other modes it loses the depth noticeably.
2) In "All", "Sel1" and "Sel2" modes GEB works GREAT! Roman brick (the most common problem) has been successfully "GEB"-ed.
3) The first problem!
In "Sel1" and "Sel2" modes; except iron; "discriminated" were also the larger Roman coin "Sestertius" (a highly desirable find) as well as a bronze applique/buckle (also a desirable find).
While the smaller Roman coin "Antoninianus" was well detected, albeit with a reduced range.
This is a BIG PROBLEM! This means that some bronze coins will be successfully found and some will not!?
4) Second problem!
In the second part of the video, you will see a nail from the 5th century. It was successfully discriminated only when directed longitudinally towards the center of the coil.
When placed sideways; "discrimination" does not work and is detected.
This is also a BIG PROBLEM! Because in the fields where there are ancient coins; there are too many similar iron objects like that nail.

Conclusion:
This kind of detector is, of course, a step forward and an improvement compared to the previous PI detectors that I made. Because it has a very good GEB.
But when it comes to "discrimination"... I'm afraid there will be a lot of trouble!
Now that I have listed all the details, I would like to hear your opinion and possibly tips and ideas; how to improve the part about discrimination...
And here's the video:

[pito]

It was successfully discriminated only when directed longitudinally towards the center of the coil.
When placed sideways; "discrimination" does not work and is detected. = do you have 2 coils ?

albeit with a reduced range. = try different MOSFET to increase Tx power, IRFZ44 and IRF510.
From which distance from the coil you can see signal changes for coins on oscilloscope on U11 pin #2 and #6 ?

Video test - move the objects side to side, that what you do when you do searching.

[ivconic]

No, only one, monocoil is used.
Former is 3D printed for "Omega coil" and I just used it to speed up that trivial task.
Mosfet is IRF840. (Thanks Moodz for wasting my money on 8x IRF840 mosfets!!!) LOL
Reduced range is because of the mixing two channels.
In All Metal mode it is twice the deeper from what you see on video.
I just didn't record the All Metal mode, it was not in my primary focus right now.

[pito]

High voltage on the coil is ?

Tx power @50 cm

[ivconic]

Dunno...

[pito]

look attachment post #407

[Carl-NC]

What you describe is normal for subtractive GB PI designs. GB mode always loses depth because of the signal subtraction. The GB subtraction always results in a target hole exactly at the GB point. Below the GB point are low conductors, above the GB point are high conductors. Nails fall into the high conductor range because of their permeability, so if you mute the high conductor range to get rid of nails then you will also get rid of high conductor coins and such.

There are ways to improve this, by using multi-TX periods or multi-RX sampling to create 2 or more GB channels. But this only gets rid of the target hole, it does not enable decent discrimination. You can pseudo-discriminate by using an IB coil and sampling the ON-time response to get a ferrous/non-ferrous indication. This is what ML does and it still isn't all that great, but better than nothing.

You now see the fundamental problems with PI detectors. It is what everybody is trying to solve.

[ivconic]

What you describe is normal for subtractive GB PI designs. GB mode always loses depth because of the signal subtraction. The GB subtraction always results in a target hole exactly at the GB point. Below the GB point are low conductors, above the GB point are high conductors. Nails fall into the high conductor range because of their permeability, so if you mute the high conductor range to get rid of nails then you will also get rid of high conductor coins and such.

There are ways to improve this, by using multi-TX periods or multi-RX sampling to create 2 or more GB channels. But this only gets rid of the target hole, it does not enable decent discrimination. You can pseudo-discriminate by using an IB coil and sampling the ON-time response to get a ferrous/non-ferrous indication. This is what ML does and it still isn't all that great, but better than nothing.

You now see the fundamental problems with PI detectors. It is what everybody is trying to solve.

Yes, that's right, nothing better than a practical example to understand the whole story.
Although, over the years I have had several PI detectors from reputable manufacturers, where I could see all of that present.
In this particular case; I'm not interested in the full "Disc scale", but only the rank group of findings that are present here in my field.
And that would be various bronze coins, silver and gold coins... and that's it.
But unfortunately, in that group of findings there are all kinds of examples of both low and high conductors... on both sides of the "hole" or at the very place of the "hole".
What can be seen on the video. The Sestertius is a much better conductor than the Antoninian as is the "thick" applique/buckle.
By the way... such a Sestertius Deus sees with VDI number 98-99! Which in most cases is the number for "thick" iron!
I read the previous threads too, followed everything. I've already heard all that from a few of you.
Of course, for a full understanding of the whole story; it was necessary to make this and to familiarize myself with everything in practice.
I don't know if there is an easy solution, I believe there isn't.
This afternoon I gave a lot of thought to the introduction of the third channel. To have two "holes", one fixed and the other "movable".
Or should I give it up and try something else, something similar to what I've already done at IGSL...
I'll see... you described the situation very well. It is difficult to find even one counterargument.